Engine exhaust structure

ABSTRACT

A temperature regulating material  31  for regulating a temperature of an exhaust manifold  11  is provided such that individual parts of the exhaust manifold  11  are uniformed in temperature. Heat transfer materials  31 A with high thermal conductivity are layered as the temperature regulating material  31  on a cover member  25  at an area corresponding to a high-temperature area HT of the exhaust manifold  11 . Heat shield materials  31 B are layered as the temperature regulating material  31  on the cover member  25  at an area corresponding to the low-temperature area LT of the exhaust manifold  11 . A heat dissipation material  31 C as the temperature regulating material  31  coats an outer surface of the area of the cover member  25  corresponding to the high-temperature area of the exhaust manifold  11.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an engine exhaust structure.

2. Description of the Related Art

At a middle portion of exhaust passage in an automobile engine, anexhaust manifold, a catalytic converter and a muffler are intervened inthis order from the upstream side. Exhaust gases from the engine arecollected in the exhaust manifold, purified through the catalyticconverter, muffed by the muffler, and then emitted to the outside.

Many mainstream catalytic converters purify exhaust gases by means of athree-way catalyst. However, those catalytic converters using athree-way catalyst have a problem that unpurified exhaust gases areemitted to the outside unless a catalyst temperature reaches an activetemperature or higher.

For this reason, there have been proposed engine exhaust structures toshorten the time between when an engine is started and when a catalystreaches an active temperature or higher, in which a catalyst converteris provided as closely to the collecting part of an exhaust manifold aspossible to facilitate a catalyst temperature rise, or in which a flowpath of exhaust gases in an exhaust manifold has a two-tiered structurewith an inner member and an outer member to form a heat shield spacebetween the two members for prevention of a temperature decrease ofexhaust gases in the exhaust manifold (refer to Patent Document 1, forexample).

Additionally, there is proposed a sound insulation cover attached to anexhaust manifold (for example, refer to Patent Document 2). Theinvention described in Patent Document 2 is intended to cut noise froman engine and protect electronic devices and their harnesses disposed inan engine room from an exhaust manifold at a high temperature.Noise-absorbing materials are layered on the sound insulation cover andact as a heat shield. This accelerates an increase in an ambienttemperature in the surroundings of the exhaust manifold, therebypromoting the activation of the catalyst.

Patent Document 1 Japanese Patent Application No. 2005-76605 PatentDocument 2 Japanese Patent Application No. 7-119458

An exhaust manifold is not at a uniform temperature in the whole. Forexample, the collecting part and its nearby areas become at highertemperature than the other areas because exhaust gases are collected inthose areas from individual cylinders. For this reason, an exhaustmanifold is designed to offer thermal resistance with reference totemperatures of the collecting part and its nearby areas. However, thisdesign requires the use of highly heat-resistant and expensive metalmaterials even for areas at low temperatures as well as the collectingpart and its nearby areas, although the areas at low temperature are notneeded to be as heat-resistant as the areas at high temperatures. Thiscauses higher costs of manufacturing exhaust manifolds. In particular,if the collecting part and the branched pipe are two-tiered or arecovered with a cover member for facilitation of the catalyst temperatureduring a warm-up and higher performance of exhaust gas purification aswith the inventions described in Patent Documents 1 and 2, theperformance of exhaust gas purification will be enhanced during thewarm-up. Instead, the whole exhaust manifold needs to be formed fromhighly nickel-containing stainless, for example, which is excellent inheat resistance but is very expensive, because the collecting part andits nearby areas are excessively become high in temperature after thewarm-up. This leads to a significant increase in costs of manufacturingexhaust manifolds.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an engine exhauststructure which contributes to a decrease in manufacturing costs ofexhaust manifolds while offering sufficient heat-resistant properties ofan exhaust manifold, by regulating uniformly the temperatures ofindividual parts of the exhaust manifold.

An engine exhaust structure in the present invention is provided with atemperature regulating material for regulating a temperature of anexhaust manifold such that individual parts of the exhaust manifold areuniformed in temperature.

In the exhaust structure, the temperature regulating material regulatesa temperature of an exhaust manifold in such a manner that individualparts of the exhaust manifold are uniformed in temperature, therebypreventing a local temperature rise in the exhaust manifold.Accordingly, with lower requirements for the heat-resistant propertiesof an exhaust manifold, it is possible to form an exhaust manifold froma metal material which is somewhat less heat-resistant but is availableat an inexpensive price, resulting in a decrease in costs ofmanufacturing exhaust manifolds.

In a preferred embodiment, a cover member may be provided to cover theexhaust manifold, and heat transfer materials with high thermalconductivity may be layered as the temperature regulating material onthe cover member at an area corresponding to a high-temperature area ofthe exhaust manifold. In this case, heat from the area of the covermember corresponding to the high-temperature area of the exhaustmanifold is efficiently transferred by the heat transfer materials to anouter panel side of the cover member, thereby facilitating heatdissipation from the area to the outside. This retards the increase ofan ambient temperature in the surroundings of the high-temperature areaof the exhaust manifold, which prevents a local temperature rise in thewhole exhaust manifold. By the prevention of local temperatureelevation, it is possible to form an exhaust manifold from aninexpensive metal material, which leads to a reduction in manufacturingcosts of exhaust manifolds, as stated above. Further, since the exhaustmanifold is covered with the cover member, a temperature rise in thewhole exhaust manifold is facilitated, a temperature rise in a catalystin a catalytic converter is accelerated, and the time required for thecatalyst to reach an active temperature or more can be shortened toimprove the performance of exhaust gas purification.

In another preferred embodiment, a cover member may be provided to coverthe exhaust manifold, and heat shield materials may be layered as thetemperature regulating material on the cover member at an areacorresponding to a low-temperature area of the exhaust manifold. In thiscase, the heat shield materials prevent the dissipation of heat to theoutside from the area of the cover member corresponding to thelow-temperature area of the exhaust manifold. This facilitates a raisein an ambient temperature in the surroundings of the low-temperaturearea of the exhaust manifold, and regulates uniformly the temperaturesof the individual parts of the exhaust manifold, thereby preventing alocal temperature rise in the whole exhaust manifold. Accordingly, it ispossible to form an exhaust manifold from an inexpensive metal materialand to reduce the costs of manufacturing exhaust manifolds, as statedabove. Further, since the exhaust manifold is covered with the covermember, a temperature rise in the whole exhaust manifold is facilitated,a temperature rise in the catalyst of the catalytic converter isaccelerated, and the time required for the catalyst to reach an activetemperature or more can be shortened to improve the performance ofexhaust gas purification. Moreover, the prevention of heat dissipationfrom the cover member by the heat shield materials allows the exhaustmanifold to be regulated in temperature. This causes the heat of exhaustgases to efficiently act on the catalytic converter, therebyaccelerating a temperature rise in the catalyst.

In another preferred embodiment, a cover member may be provided to coverthe exhaust manifold, and temperature regulating materials may belayered as the temperature regulating material on the cover member, anarea of each of the temperature regulating materials corresponding tothe high-temperature area of the exhaust manifold being made higher inthermal conductivity than an area of each of the temperature regulatingmaterials corresponding to the low-temperature area of the exhaustmanifold. In this case, the temperature regulating materials facilitateheat dissipation to the outside from the outer panel of the cover memberat a high-temperature area, and suppress heat dissipation to the outsidefrom the outer panel of the cover member at a low-temperature area. Thisregulates uniformly an ambient temperature in the surroundings of theexhaust manifold with further efficiency, regulates uniformly thetemperatures of the individual parts of the exhaust manifold, andprevents a local temperature rise in the exhaust manifold. Accordingly,it is possible to form the exhaust manifold from an inexpensive metalmaterial and reduce the costs of manufacturing exhaust manifolds, asstated above. Further, since the exhaust manifold is covered with thecover member, a temperature rise in the whole exhaust manifold isfacilitated, a temperature rise in the catalyst in the catalyticconverter is accelerated, and the time required for the catalyst toreach an active temperature or more can be shortened to improve theperformance of exhaust gas purification.

In another preferred embodiment, a cover member may be provided to theexhaust manifold and a heat dissipation material as the temperatureregulating material may coat an outer surface of the area of the covermember corresponding to the high-temperature area of the exhaustmanifold. In this case, heat from the area of the cover membercorresponding to the high-temperature area of the exhaust manifold isefficiently dissipated to the outside by the heat dissipation material.This suppresses an increase in an ambient temperature in thesurroundings of the high-temperature area of the exhaust manifold,regulates uniformly the temperatures of the individual parts of theexhaust manifold, and prevents a local temperature rise in the exhaustmanifold. Accordingly, with lower requirements for the heat-resistantproperties of an exhaust manifold, it is possible to form an exhaustmanifold from an inexpensive metal material, resulting in a decrease incosts of manufacturing exhaust manifolds, as described above.

In another preferred embodiment, a cover member may be provided to coverthe exhaust manifold, and heat transfer materials with high thermalconductivity may be layered as the temperature regulating materialbetween the cover member and the high-temperature area of the exhaustmanifold. In this case, heat from the high-temperature area of theexhaust manifold is efficiently transferred to the cover member side bythe heat transfer materials, regulates uniformly temperatures of theindividual parts of the exhaust manifold, and prevents a localtemperature rise in the exhaust manifold. Accordingly, with lowerrequirements for the heat-resistant properties of an exhaust manifold,it is possible to form an exhaust manifold from an inexpensive metalmaterial, resulting in a decrease in costs of manufacturing exhaustmanifolds, as stated above.

In another preferred embodiment, a cover member may be provided to coverthe exhaust manifold, and heat shield materials may be layered as thetemperature regulating material on the area of the cover membercorresponding to the low-temperature area of the exhaust manifold. Inthis case, the heat shield materials prevent the dissipation of heat tothe outside from the area of the cover member corresponding to thelow-temperature area of the exhaust manifold. This facilitates a rise inan ambient temperature in the surroundings of the low-temperature areaof the exhaust manifold, and regulates uniformly the temperatures of theindividual parts of the exhaust manifold, thereby preventing a localtemperature rise in the exhaust manifold. Accordingly, with lowerrequirements for the heat-resistant properties of an exhaust manifold,it is possible to form an exhaust manifold from an inexpensive metalmaterial and reduce the costs of manufacturing exhaust manifolds, asstated above.

In another preferred embodiment, a cover member may be provided to coverthe exhaust manifold, and temperature regulating materials may belayered as the temperature regulating material between the cover memberand the exhaust manifold, an area of each of the temperature regulatingmaterials corresponding to the high-temperature area of the exhaustmanifold being made higher in thermal conductivity than an area of eachof the temperature regulating materials corresponding to thelow-temperature area of the exhaust manifold. In this case, thetemperature regulating materials facilitate heat transfer from theexhaust manifold to the cover member at the high-temperature area, andsuppress heat transfer from the exhaust manifold to the cover member atthe low-temperature area. This regulates uniformly temperatures of theindividual parts of the exhaust manifold, and prevents a localtemperature rise in the exhaust manifold. Accordingly, with lowrequirements for the heat-resistant properties of an exhaust manifold,it is possible to form an exhaust manifold from an inexpensive metalmaterial, resulting in a decrease in costs of manufacturing exhaustmanifolds, as stated above.

In another preferred embodiment, the exhaust manifold may have atwo-tiered structure with an inner member and an outer member in part orin all, and heat transfer materials with high thermal conductivity maybe layered as the temperature regulating material on thehigh-temperature area of the exhaust manifold between the inner memberand the outer member. In this case, at the high-temperature area of theexhaust manifold, the heat transfer materials transfer heat from theinner member to the outer member, facilitate the heat dissipation fromthe outer member, regulate uniformly the temperatures of the individualparts of the exhaust manifold, and prevent a local temperature rise inthe exhaust manifold. Accordingly, with lower requirements for theheat-resistant properties of an exhaust manifold, it is possible to forman exhaust manifold from an inexpensive metal material, resulting in adecrease in costs of manufacturing exhaust manifolds, as stated above.Further, since the exhaust manifold has a two-tiered structure with theinner member and the outer member, a temperature rise in the whole innermember is facilitated, a temperature rise in the catalyst in thecatalytic converter is accelerated, and the time required for thecatalyst to reach an active temperature or more can be shortened toimprove the performance of exhaust gas purification.

In another preferred embodiment, the exhaust manifold may have atwo-tiered structure with an inner member and an outer member in part orin all, and heat shield materials may be layered as the temperatureregulating material on the low-temperature area of the exhaust manifoldbetween the inner member and the outer member. In this case, at thelow-temperature area of the exhaust manifold, the heat shield materialsblock heat from the inner member to suppress heat transfer to the outermember, regulate uniformly the temperatures of the individual parts ofthe exhaust manifold, and prevent a local temperature rise in theexhaust manifold. Accordingly, with lower requirements for theheat-resistant properties of an exhaust manifold, it is possible to forman exhaust manifold from an inexpensive metal material, resulting in adecrease in costs of manufacturing exhaust manifolds, as stated above.Further, since the exhaust manifold has a two-tiered structure with theinner member and the outer member, a temperature rise in the whole innermember is facilitated, a temperature rise in the catalyst in thecatalytic converter is accelerated, and the time required for thecatalyst to reach an active temperature or more can be shortened toimprove the performance of exhaust gas purification. Moreover, since theprevention of heat dissipation from the inner member by the heat shieldmaterials allows the exhaust manifold to be regulated in temperature, itis possible to cause the heat of exhaust gases to efficiently act on thecatalytic converter, thereby accelerating a temperature rise in thecatalyst.

In another preferred embodiment, the exhaust manifold may be atwo-tiered structure with an inner member and an outer member in part orin all, and temperature regulating materials may be layered as thetemperature regulating material between the inner member and the outermember, an area of each of the temperature regulating materialscorresponding to the high-temperature area of the exhaust manifold beingmade higher in thermal conductivity than an area of each of thetemperature regulating materials corresponding to the low-temperaturearea of the exhaust manifold. In this case, the temperature regulatingmaterials facilitate heat dissipation from the inner member to the outermember at the high-temperature area, and suppress heat dissipation fromthe inner member to the outer member at a low-temperature area. Thisregulates uniformly the temperatures of the individual parts of theexhaust manifold more effectively, thereby preventing a localtemperature rise in the exhaust manifold. Accordingly, with lowrequirements for the heat-resistant properties of an exhaust manifold,it is possible to form an exhaust manifold from an inexpensive metalmaterial and reduce the costs of manufacturing exhaust manifolds, asstated above. Further, since the exhaust manifold is covered with thecover member, a temperature rise in the whole exhaust manifold isfacilitated, a temperature raise in the catalyst in the catalyticconverter is accelerated, and the time required for the catalyst toreach an active temperature or more can be shortened to improve theperformance of exhaust gas purification.

In another preferred embodiment, the high-temperature area of theexhaust manifold is an area that contains at least the collecting part.The collecting part of the exhaust manifold becomes high in temperaturedue to exhaust gases collected from the individual cylinders of anengine. Therefore, when the area containing the collecting part is setas the high-temperature area and the remaining branched area is set asthe low-temperature area, the temperatures of the two areas can beregulated uniformly.

According to an engine exhaust structure in the present invention, thetemperature regulating materials regulate a temperature of the exhaustmanifold in such a manner that temperatures of the individual parts ofthe exhaust manifold are uniformed, thereby preventing a localtemperature rise in the exhaust manifold. Accordingly, with lowerrequirements for the heat-resistant properties of an exhaust manifold,it is possible to form an exhaust manifold from a metal material whichis somewhat less heat-resistant but is available at an inexpensiveprice, resulting in a decrease in costs of manufacturing exhaustmanifolds.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of main components of an engine exhauststructure;

FIG. 2 is a front view of an exhaust manifold;

FIG. 3 is a cross-sectional view of the exhaust manifold in FIG. 2 witha cover member and without temperature regulating materials, taken alongline III-III;

FIG. 4 is a view of the exhaust manifold with temperature regulatingmaterials, which is equivalent to FIG. 3; and

FIG. 5 is a front view of an exhaust manifold of another configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

First, a basic configuration of an automobile engine exhaust structurewill be discussed.

An engine 10 shown in FIG. 1 is an automobile inline four-cylinderengine. At a middle portion of an exhaust passage in the engine 10, anexhaust manifold 11, a catalytic converter 12 and a muffler (not shown)are intervened in this order from the upstream side. Exhaust gases fromthe engine 10 are collected in the exhaust manifold 11, purified throughthe catalytic converter 12, muffed by the muffler, and then emitted tothe outside.

As shown in FIGS. 1 to 3, the exhaust manifold 11 includes four branchedpipes 15 connected respectively to four exhaust ports 14 formed in acylinder head 13, a collecting pipe 16 aggregating downstream ends ofthe four branched pipes 15, and outer members 17 each covering a pair ofthe adjacent branched pipes 15.

A first tubular clearance 18 of 1.0 to 4.0 mm in thickness, for example,is provided between the outer members 17 and the branched pipes 15 alongthe almost full lengths thereof. Each of the outer members 17 is formedfrom an upper surface plate 17U and a lower surface plate 17L. The outermember 17 is assembled in such a manner as to surround the branched pipe15 by combining the upper surface plate 17U and the lower surface plate17L with the branched pipes 15 inside thereof and welding the two platestogether in a butt joint. Provided at an upstream end of each of theouter members 17 is a bifurcated part 17 a that is branched into two.Upstream ends of the branched pipes 15 are individually fitted into thebifurcated part 17 a of the outer member 17. Provided at an upstream endof the exhaust manifold 11 is an overlaid part 17 b in which theupstream end of the bifurcated part 17 a is reduced in diameter andoverlaid on the upstream end of the branched pipe 15. An attachmentsheet 19 is provided at the upstream end of the exhaust manifold 11 forattachment to the cylinder head 13. The attachment sheet 19 is providedwith four through-holes 20 corresponding to the exhaust ports 14. Byinserting and welding the overlaid parts 17 b individually into the fourthrough-holes 20, the four branched pipes 15 and the two outer members17 are combined via the attachment sheet 19. A downstream end of theouter member 17 is welded into the collecting pipe 16. A spacer member21 for preventing vibrations of the branched pipe 15 is intervenedbetween the downstream end of the branched pipe 15 and the downstreamend of the outer member 17. In addition, a flange member 22 is weldedinto a downstream end of the collecting pipe 16 for connection to anexhaust pipe on the downstream side.

Provided at both upper and lower sides of the exhaust manifold 11 arecover members 25 for blocking noise and heat from the exhaust manifold11. The upper and lower cover members 25 are each fixed to the exhaustmanifold 11 by means of a bracket member 26 provided on the exhaustmanifold 11. A second clearance 27 is provided between the exhaustmanifold 11 and the cover member 25. However, the lower cover member 25may be eliminated.

The upper and lower cover members 25 each include an outer panel 28disposed on the outer surface side and an inner panel 29 disposed on theexhaust manifold 11 side. A third clearance 30 is provided between theouter panel 28 and the inner panel 29. In the third clearance 30,sound-absorbing materials or temperature regulating materials 31 to bediscussed below are layered in close contact with the outer panel 28 andthe inner panel 29. The outer panel 28 and the inner panel 29 are madeby press-molding metal plates of stainless steel or the like. However,the inner panel 29 may be formed from general-purpose punching metal ormesh for higher sound-absorbing quality.

The present invention is characterized in that, in an exhaust structureof the engine 10 formed basically as described above, temperatureregulating materials are disposed as shown in FIG. 4, for example, forregulating uniformly temperatures of the individual parts of the exhaustmanifold 11.

The exhaust manifold 11 becomes higher in temperature from the cylinderhead 13 side to the collecting pipe 16 side. It is impossible to specifya boundary B between the low-temperature area LT and thehigh-temperature area HT as shown in FIG. 4. However, assuming that apipe length between the upstream end of the branched pipe 15 and theboundary B is L1, and that a pipe length between the boundary B and thedownstream end of the collecting pipe 16 is L2, the boundary B can beset within a range that L1/(L1+L2) becomes 20 to 35%.

As the temperature regulating material 31, a heat transfer material 31Ais tightly arranged in the high-temperature area(s) HT of one or moreselected from the first clearance 18, the second clearance 27 and thethird clearance 30. In addition, a heat shield material 31B is tightlyarranged in the low-temperature area(s) LT of one or more selected fromthe first clearance 18, the second clearance 27 and the third clearance30. Further, a heat dissipation material 31C may coat the outer surfaceof at least one of the high-temperature area HT of the exhaust manifold11 and the high-temperature area HT of the cover member 25. However, thefirst clearance 18 between the branched pipe 15 and the outer member 17acts as a heat insulating space, and therefore the heat shield material31B for the low-temperature area LT may be eliminated. Additionally, ifthe heat transfer material 31A is provided in the high-temperature areaHT of the second clearance 27, a coating of the heat dissipationmaterial 31C to the outer surface of the high-temperature area HT of theexhaust manifold 11 may be eliminated. Further, if the heat transfermaterial 31A or the heat shield material 31B is not provided in thethird clearance 30, a sound-absorbing material is to be provided in thelocation instead. The temperature regulating material 31 is only neededto be provided such that temperatures of the individual parts of theexhaust manifold 11, in particular, temperatures of the branched pipes15 and the collecting pipe 16 are uniformly regulated. The temperatureregulating material 31 may be provided to at least one of theabove-described areas.

In particular, as shown in FIG. 4, the heat transfer materials 31A areprovided to the high-temperature area HT of the first clearance 18 andthe high-temperature area HT of the second clearance 27, the heatdissipation material 31C coats the outer surface of the cover member 25,and the heat shield materials 31B are provided to the low-temperaturearea LT of the second clearance 27. Accordingly, the heat transfermaterials 31A transfer efficiently heat from the high-temperature areaHT of the exhaust manifold 11 to the cover member 25, and then the heatdissipation material 31C dissipates heat from the outer surface of thecover member 25 to the outside. Accordingly, it is possible to preventexcessively high temperatures of the downstream portions of the branchedpipes 15 and the collecting pipe 16 with most strict requirements forheat resistance, and to improve the heat-retaining properties of theupstream sides of the branched pipes 15 for accelerating a temperaturerise. This allows the branched pipes 15 and the collecting pipe 16 to beregulated in temperature uniformly as a whole.

The heat shield material 31B may use preferably a mat formed frominorganic fibers such as glass fibers, rock wool fibers, ceramic fibersor potassium titanate fibers, or organic fibers such aspoly-phenylene-benzobisoxazole (PBO) fibers.

The heat transfer material 31A may use a mat formed from metal fiberssuch as stainless fibers, steel fibers, copper fibers, brass fibers,bronze fibers or aluminum fibers, or carbon fibers such as pitch-basedcarbon fibers or PAN-based carbon fibers, or metal plating fibers. Inaddition, to seal the first clearance 18 between the outer member 17 andthe branched pipe 15 and the third clearance 30 between the outer panel28 and inner panel 29 of the cover member 25, these clearances 18 and 30may be filled with one or a mixture of any combination of carbon powder,graphitic powder, aluminum powder, copper powder, brass powder, andbronze powder. Further, any of the above-mentioned fiber materials maysupport any of the above-mentioned powders when it is formed into a mat.

The heat dissipation material 31C may appropriately use a ceramic-basedheat dissipation coating material, for example, Cooltech (made byOkitsumo Incorporated). Alternatively, a silicon- or acryl-based heatdissipation sheet may be stuck as the heat dissipation material 31C.

The temperature regulating materials 31 to be attached to differentareas may be formed from a material of the same kind or from materialsof different kinds. In this embodiment, the exhaust manifold 11 isdivided into two segments of low-temperature area LT andhigh-temperature area HT. Alternatively, the exhaust manifold 11 may bedivided into three segments of high-temperature area, medium-temperaturearea and low-temperature area, or more segments, such that theindividual parts of the exhaust manifold 11 are uniform in temperature.Further, the temperature regulating material 31 may change gradually orcontinuously in heat shield properties and/or heat transfer propertiesto regulate a temperature of the exhaust manifold 11 in a more detailedmanner.

The present invention is also applicable to an exhaust structure for theengine 10 without the outer member 17 and an exhaust structure for theengine 10 without the cover member 25. For an exhaust structure withoutthe outer member 17, the heat shield material 31B or heat transfermaterial 31A is disposed in at least one of the second clearance 27between the cover member 25 and the branched pipe 15 and the thirdclearance 30 between the outer panel 28 and inner panel 29 of the covermember 25. Alternatively, the heat dissipation material 31C coats theouter surfaces of the branched pipe 15 and collecting pipe 16, or theouter surface of the cover member 25 at the high-temperature area HT.For an exhaust structure without the cover member 25, the heat shieldmaterial 31B or the heat transfer material 31A is disposed in the firstclearance 18 between the outer member 17 and the branched pipe 15, theheat dissipation material 31C is disposed on the outer surfaces of theouter member 17 and collecting pipe 16. Further, if the cover member 25is a cover member without the third clearance 30 formed between theouter panel 28 and the inner panel 29, or if the cover member 25 is acover member formed from a single panel, the heat shield material 31B orthe heat transfer material 31A is disposed in the first clearance 18between the outer member 17 and the branched pipe 15 and is disposed inthe second clearance 27 between the cover member and the branched pipe15, and the heat dissipation material 31C coats the outer surface of theexhaust manifold 11 or the outer surface of the cover member at thehigh-temperature area HT.

The present invention is applicable to any configuration of the exhaustmanifold 11. For example, as shown in FIG. 5, the present invention maybe applied to an exhaust manifold 41 including four branched pipes 40 ofdifferent lengths. Additionally, the present invention can be applied toan exhaust manifold with the outer member 17 surrounding the individualbranched pipes 15. For provision of such an outer member surrounding theindividual branched pipes 15, the outer member may be formed by weldingthe upper surface plate and the lower surface plate together, or theouter member 17 formed from a pipe member larger in diameter than thebranched pipe 15 may be attached to the outside of the branched pipe 15.Moreover, the present invention can be applied to exhaust structures forinline multi-cylinder engines and V-type multi-cylinder engines as wellas those for the inline four-cylinder engine 10.

1. An engine exhaust structure provided with a temperature regulating material for regulating a temperature of an exhaust manifold such that individual parts of the exhaust manifold are uniformed in temperature.
 2. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and heat transfer materials with high thermal conductivity are layered as the temperature regulating material on the cover member at an area corresponding to a high-temperature area of the exhaust manifold.
 3. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and heat shield materials are layered as the temperature regulating material on the cover member at an area corresponding to a low-temperature area of the exhaust manifold.
 4. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and temperature regulating materials are layered as the temperature regulating material on the cover member, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold.
 5. The engine exhaust structure according to claim 1, wherein a cover member is provided to the exhaust manifold and a heat dissipation material as the temperature regulating material coats an outer surface of the area of the cover member corresponding to the high-temperature area of the exhaust manifold.
 6. The engine exhaust structure according to claim 1, wherein a cover is provided to cover the exhaust manifold, and heat transfer materials with high thermal conductivity are layered as the temperature regulating material between the cover member and the high-temperature area of the exhaust manifold.
 7. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and heat shield materials are layered as the temperature regulating material on an area of the cover member corresponding to a low-temperature area of the exhaust manifold.
 8. The engine exhaust structure according to claim 1, wherein a cover member is provided to cover the exhaust manifold, and temperature regulating materials are layered as the temperature regulating material between the cover member and the exhaust manifold, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold.
 9. The engine exhaust structure according to claim 1, wherein the exhaust manifold has a two-tiered structure with an inner member and an outer member in part or in all, and heat transfer materials with high thermal conductivity are layered as the temperature regulating material on the high-temperature area of the exhaust manifold between the inner member and the outer member.
 10. The engine exhaust structure according to claim 1, wherein the exhaust manifold has a two-tiered structure with an inner member and an outer member in part or in all, and heat shield materials are layered as the temperature regulating material on the low-temperature area of the exhaust manifold between the inner member and the outer member.
 11. The engine exhaust structure according to claim 1, wherein the exhaust manifold has a two-tiered structure with an inner member and an outer member in part or in all, and temperature regulating materials are layered as the temperature regulating material between the inner member and the outer member, an area of each of the temperature regulating materials corresponding to the high-temperature area of the exhaust manifold being made higher in thermal conductivity than an area of each of the temperature regulating materials corresponding to the low-temperature area of the exhaust manifold.
 12. The engine exhaust structure according to claim 1, wherein the high-temperature area of the exhaust manifold is an area that contains at least the collecting part. 